Earl,
I choose to have my cab dipped, it gets in ALL the tight places you cannont hope to reach by other methods. The rust you see on the cab is from the body man NOT cleaning and priming as promised it rusted in his shop (*%$tard). I have picture of the process here.
http://rides.webshots.com/album/418332987uAZJiR Before I had the cab dipped, I tried Soda blasting, it does not remove the heavy rust so you are still faced with the problem, not to mention the roof area if you have a double roof as the 60-66 series trucks have. Soda pictues here.
http://rides.webshots.com/album/414823796vWvHlX